As packaged semiconductor devices become smaller and more complex, their handling, installation and removal from electronic circuits has become more difficult. Not only are the devices difficult to grasp, hold and position properly, there is increasing risk of damage to the packaged semiconductor device, particularly the delicate leads. As a result, there has been developed a considerable body of technology devoted to careful handling of semiconductor devices.
For example, U.S. Pat. No. 3,516,142 to DeRose et al, discloses a hand tool for gently inserting and removing semiconductor flatpacks to and from socket connections. A rod-shaped tool for lifting single pin-supported miniature electronic packages from sockets is taught in U.S. Pat. No. 3,832,764 to Fletcher et al. Semiautomatic devices for removing solid state, multicontact electrical circuit devices, such as dual-in-line packages (DIPs) which have been soldered in place on printed circuit boards are seen in U.S. Pat. No. 3,731,866 to Mason et al and U.S. Pat. No. 4,136,444 to Durney.
One particular area of concern in semiconductor device handling concerns the removal of large numbers of integrated circuit (IC) packages from a burn-in board after a burn-in operation. The burn-in operation is one of the last steps in the fabrication of ICs. In a conventional burn-in procedure, a plurality, typically forty, eighty or more, of semiconductor devices are mounted in sockets mounted on a burn-in board. The sockets are electrically connected through the thin copper foil leads of the printed circuit board, to which appropriate input logic and power signals are applied so that the ICs receive the appropriate logic and power signals during the burn-in process. During the burn-in process, the semiconductor devices are subjected to elevated temperatures in the range of 90.degree. C. to 125.degree. C. or more for a predetermined period of time, to test them under normal usage, or even abusive conditions.
Ordinarily, the sockets in the typical burn-in board are arranged in a plurality of parallel rows with space provided between adjacent rows of sockets. After the completion of the burn-in procedure, the individual IC packages are removed by the use of a hand tool, such as those previously noted, which lifts the IC packages from the sockets in which they were mounted during the burn-in procedure.
The use of most conventional hand removal tools to remove the heated integrated circuit packages from the board is a time- and labor-intensive, and thus costly operation. In addition, even when the semiconductor devices are removed from the burn-in board with care, the leads of at least some of the packages are invariably bent. If these bent leads are undetected, the IC will fail electrical tests; if the bent leads are detected, additional time and labor is required to restore the bent leads to their proper orientation with respect to the package. The process of directly removing the DIPs or IC packages is also bothersome to the worker since the packages are still hot when they are removed from the burn-in tray by conventional direct hand tools.
Structures offered as at least partial solutions to the problems associated with unloading burn-in boards include the multi-pronged clamp and pull device of U.S. Pat. No. 4,324,040 to Gottlieb, which removes all the IC packages from the burn-in board simultaneously. While the Gottlieb device is no doubt effective, it is evident that the multi-pronged clamp device and the IC packages enveloped thereby must be pulled away from the burn-in board very evenly. Any twisting or warping of the removal tool could result in damage to the burn-in board, the IC devices or the leads thereto or the removal device itself. U.S. Pat. No. 4,420,880 to Mielke reveals an elongated, wedge-shaped extraction tool for removing DIPs from a burn-in board, or the like, entire rows at a time and then slipping them into U-shaped packing tubes. This device is also useful, but because of its pointed tip, requires extreme care on the part of the operator to avoid severely damaging the leads extending from the IC packages by slight misalignment of the tool.
A more recent package design is a "leadless chip carrier" or LCC, also known as quadpacks because of the leads on all four sides of the package instead of on only two sides as in the case of the DIPs. The term "leadless" is not strictly accurate, because the leads are present along the outside surface edge of the square or rectangular, flat plastic or ceramic package. However, no leads extend out or away from the package body, but instead are relatively protected in place along the edges of the package. Typically, special sockets are required to make connection to LCCs. One popular type of LCC socket has a box-like configuration with an aperture in the center into which the LCC fits. Within the aperture are a number of leads spring-biased toward the center of the aperture designed to make electrical contact with the LCC leads as well as hold the LCC physically in place inside the socket. The spring-biased leads are held away from their interior position by pressing down on the lid of the socket, and the LCC may be removed from the aperture.
When these spring-biased semiconductor device sockets are used in large quantities on burn-in boards, a problem arises with how to get the LCCs out of the sockets faster than one at a time. One method is to use an array of tiny vacuum fingers to seize the LCCs out of the apertures as the socket lids are pressed down. A drawback to this technique is that the vacuum equipment would have to be complicated and expensive to build and operate. A straightforward approach would be to flip the burn-in board over and press it down in a catch tray and release all of the LCCs at once. The problem with this latter technique is that considerable pressure would have to be used to simultaneously release all of the LCCs, which may require expensive machinery. In addition, the pressure must be applied evenly to avoid warping the burn-in board and thus damaging the delicate copper leads thereon, or the spring-biased sockets.
The present invention solves these problems with a parallel roller tool. Two patents have been found which employ rollers to remove electronic components. U.S. Pat. No. 4,307,510 to Sawyer et al, teaches a screwdriver-like device mounted on wide rollers. The blade of the device serves to pry out the end of printed circuit cards mounted in a card rack with the rollers serving as a fulcrum. U.S. Pat. No. 4,362,991 to Carbine reveals an automatic coordinate axis system that runs on rollers for testing each IC package of the flat pack type arranged within a test tray full of such devices.